Friction acting on a wheel that is initially at rest

  • Context: High School 
  • Thread starter Thread starter geko11
  • Start date Start date
  • Tags Tags
    Friction Rest Wheel
Click For Summary

Discussion Overview

The discussion revolves around understanding the forces acting on a wheel that is initially at rest, specifically focusing on the role of static friction and rolling resistance in initiating and maintaining motion. Participants explore the application of various equations related to friction and acceleration in a mechanical context.

Discussion Character

  • Exploratory
  • Technical explanation
  • Mathematical reasoning

Main Points Raised

  • One participant suggests using the static friction equation (F = u*Normal) to determine the force needed to start the wheel rolling and the rolling friction force equation to maintain motion.
  • Another participant clarifies that while static friction is necessary to get the wheel rolling, the actual friction required depends on the desired acceleration, which can be anywhere from 0 to the maximum static friction value.
  • A later reply indicates that Newton's second law (F = m*a) should be used to find the force when acceleration is known, and emphasizes the need for rotational dynamics (Torque = I*alpha) for rotational motion.
  • One participant points out that the opposing force during motion is due to rolling resistance rather than static friction, noting that rolling resistance is related to the deformation of the rolling object.

Areas of Agreement / Disagreement

Participants generally agree on the necessity of static friction to initiate motion, but there is some disagreement regarding the roles of static friction and rolling resistance in the context of forces acting on the wheel. The discussion remains unresolved regarding the precise application of these concepts.

Contextual Notes

Participants mention various equations and concepts without fully resolving the relationships between static friction, rolling resistance, and the forces involved in both translation and rotation. There is a lack of consensus on the best approach to calculate the forces required for specific scenarios.

geko11
Messages
3
Reaction score
0
Hello everyone,

I have a project of mine where I need to find out the force that acts on a wheel to start it rolling and keep it rolling so I can then select the correct motor and gear box.

I have not had to do this kind of physics for years and I am having trouble with this problem:

If a wheel is initially at rest then the standard static friction equation would apply (F = u*Normal) initially to find the force to get the wheel moving and then the rolling friction force equation would be used to work out the force required to keep it going?

or

Because it is a wheel the initial and ongoing friction would be determined by using the rolling static friction equation in both cases?

I am really confused here and would really appreciate the help.

Thanks. :)
 
Physics news on Phys.org
geko11 said:
If a wheel is initially at rest then the standard static friction equation would apply (F = u*Normal) initially to find the force to get the wheel moving and then the rolling friction force equation would be used to work out the force required to keep it going?
To get the wheel rolling requires static friction (assuming no slipping). But μN gives the maximum amount of friction available to you; the actual friction required depends on the acceleration you are trying to impart. (The actual static friction could be anything from 0 to the maximum value.)
 
ok thanks, so F=uN is max force.

what equation do I use if I have an acceleration in mind to find the force?
 
geko11 said:
ok thanks, so F=uN is max force.
Right.
what equation do I use if I have an acceleration in mind to find the force?
Newton's 2nd law for rotation and translation.
 
F=m*a...
now I feel like an idiot, but I am glad I asked.
thanks doc your a Legend.
 
geko11 said:
F=m*a...
That will do for translation; for rotation, use Torque = I*alpha.
 
rcgldr said:
The opposing force is due to rolling resistance, not static friction.
To accelerate the wheel from rest, static friction is required.
 

Similar threads

High School Static friction needed for rolling without slipping
  • · Replies 4 ·
Replies
4
Views
2K
Undergrad Torque required from powered roller to rotate cylinder
  • · Replies 19 ·
Replies
19
Views
3K
Undergrad Rolling Without Slipping
  • · Replies 59 ·
2
Replies
59
Views
5K
High School How does the front wheel have no friction?
  • · Replies 27 ·
Replies
27
Views
4K
Undergrad Direction of friction of each wheel and total moment when a car turns
  • · Replies 6 ·
Replies
6
Views
3K
Undergrad Solving Wheel Coming to a Stop: FBD, Friction & Hysteresis
  • · Replies 22 ·
Replies
22
Views
5K
High School Why is static friction necessary for pure rolling?
  • · Replies 4 ·
Replies
4
Views
3K
High School How come friction can make a car turn?
  • · Replies 10 ·
Replies
10
Views
3K
Undergrad Rolling friction and static friction....
  • · Replies 2 ·
Replies
2
Views
2K
High School Questions about momentum and force as well as normal force/friction
  • · Replies 35 ·
2
Replies
35
Views
5K